Precision

  Precision describes the reproducibility of measurements in other words, the closeness of results that have been obtained in exactly the same way. Generally, the precision of a measurement is readily determined by simply repeating the measurement on replicate samples.

  Three terms are widely used to describe the precision of a set of replicate data: standard deviation, variance, and coefficient of variation. These three are functions of how much an individual result x_i differs from the mean, called the deviation from the mean d_i.